Winter Quarters, at Low Ridge Haven Options

[bigdipper]

250 is the figure at which they'd have to do nothing but survive as I understand it.

Doug

Thanks. Revisiting "oppy vs spirit power consumption" thread in Feb '06

300 watt hrs/sol min to function
275 watt hrs/sol electronics start to go?
<275 watt hrs/sol for extended period [emoticon for "I can't watch"]

200 sols from now I'll look back and say "o me of little faith" for worrying.
GO Spirit GO! I mean CHARGE Spirit CHARGE!.

EDIT: (I just noticed the Whrs thread in the tech forum, How could I have missed it?)

[helvick]

<275 watt hrs/sol for extended period [emoticon for "I can't watch"]

200 sols from now I'll look back and say "o me of little faith" for worrying.
GO Spirit GO! I mean CHARGE Spirit CHARGE!.

We'll see.

The problem with estimating power is that we don't really know how much dust is settling from day to day. There are many ways to do this but I generally stick to the pre-flight estimate of 0.18% loss of power per sol which should be a bit on the high side for this time of the year (beause the atmosphere is relatively clear of dust as the winter solstice approaches) but it generally has held out well over time.

The estimates I listed earlier in the thread were based on the previous most recently reported power generation number (310whr on Sol 877/June 21). Using 0.18% dust loss that predicts a minimum power generating capability of 273whr between September 5 and 11. That 310 whr number was about 6 whr higher than I had anticipated on that day, it's not much but it is relevant so bear with me.

Working from the 27 May reported number of 330 whr I had calculated that we would have hit 290whr on 7 July with 0.18% dust loss so over that period of time the estimated dust loss is pretty accurate. Extrapolating that out gives a minimum power capability of 268whr from the 16th to 24th of September.

However the worst case is when you take the 310 whr that was reported for the 21st of June and adjust the dust loss parameter so that the chart gives 290whr on July 7. To bring the two into agreement I have to adjust the power degradation due to dust rate to 0.33%. Extrapolating that out yields a minimum power level of 236whr between October 15 and Nov 1. That would be very bad.

I don't really think that that worst case is actually true though because it would require that the dust deposition rate has increased dramatically which is not very likely. Overall atmospheric dust levels (as measured by Tau) will only start to rise again approximately 90 or so Sols after the solstice. Winds pick up _before_ that though and there is some indication that dust deposition on the panels increased around 30 or so sols after the last winter Solstice. Since we're still 28 Sols from the Solstice I think it is way too early for us to be seeing the winds pick up sufficiently to start to influence the power generating capability. I suspect that the 310 whr number for June 21 was just rounded up for reporting in order to make a neat number.

Oh and just think how bad things would be without the 15degree tilt she got by backing up onto that stone.

Anyway we'll see soon enough.

[bigdipper]

We'll see.

Working from the 27 May reported number of 330 whr I had calculated that we would have hit 290whr on 7 July with 0.18% dust loss so over that period of time the estimated dust loss is pretty accurate. Extrapolating that out gives a minimum power capability of 268whr from the 16th to 24th of September.

However the worst case is when you take the 310 whr that was reported for the 21st of June and adjust the dust loss parameter so that the chart gives 290whr on July 7. To bring the two into agreement I have to adjust the power degradation due to dust rate to 0.33%. Extrapolating that out yields a minimum power level of 236whr between October 15 and Nov 1. That would be very bad.

...

Thanks again, Helvick.

1000 sols or Bust!

ps. Is there a new HPC forthcoming? At least one fan is anxiously awaiting your next release

[Jeff7]

Maybe Spirit will have to truly hibernate this winter. It's in a valley, which probably isn't the best place to be for a cleaning of any sort, regardless of it being summer or winter.

[diane]

I'm not sure what "hibernate" means in technical terms, given the need to keep some heat going inside Spirit. Long-term deep sleep probably isn't a viable plan, but it would be interesting to know what "minimum activity" would consist of.

In the mean time, I'd guess that the first priority is to finish up as many parts of the long-term observations as they can (McMurdo pan, Halley, anything else), then hunker down for survival.

[djellison]

it would be interesting to know what "minimum activity" would consist of.

9am Wakeup and Tau Observation
10am HGA uplink of commands
1030am Sleep
4pm Wakeup, Tau Observation and Odyssey UHF Pass
4.30pm Sleep.


Basically - that's it. You could even skip the morning uplink and uplink via UHF in the PM Odyssey pass

Doug

[helvick]

Is there a new HPC forthcoming? At least one fan is anxiously awaiting your next release

It is way past time for an updated posting of the full spreadsheet - I have to clean it up quite a bit as the working file has degenerated into a bit of a mess over the past six months. If I get enough time this week to tidy it up again I'll post the updated version.

[Guest_Sunspot_*]

I'm sure I read somewhere they had special plans in place if power should fall to a dangerously low level. It didn't say what they were though lol.

[diane]

Just a guess, but those emergency power plans probably aren't very pretty. It probably means sacrificing parts of the rover for the remaining mission time, such as turning off heaters in the wheels. Then turning off other instruments. The pancam and atmospheric observations would probably be the last to go.

[djellison]

Yes - just boil it right down to a wake-up.... LGA beep.....go to sleep - nothing more.

Heaters to wheels etc will be off at the moment anyway - they only use them when driving.

Doug

[tty]

Actually the wake-up period must be long enough to use up most of the available power since that is what keeps the WEB at a reasonable temperature. Consequently as much as possible of the action should be inside the WEB, and preferably in the afternoon so the minimum temperature (in the morning hours) does not become low enough to kill the avionics. Also it is vital to have enough power left in the batteries in the evening for battery heating if required during the late night - early morning. Otherwise it's EOM. I'm uncertain whether this is compatible with "deep sleep" since I don't know whether the battery heating works when the battery is offline. Possibly the battery heater is internal to the battery itself and cuts in even when it is offline? Anybody know?

tty

[Jeff7]

Opportunity did alright though with regular use of deep sleep.

[djellison]

I think the conservative strategy would be to save every ounce of power to ensure you have every Whr the overnight heaters could ask for when the sun sets. It's a risk to invest that power in using the rover late in the day to warm up the WEB. More sensible to save the power, and use it in the most efficient way of turning electricity to heat...the heaters, instead of the heat as a biproduct of other useage.

Oppy could handle deep sleep because they had enough power to really heat up the WEB by doing 'stuff' before the end of the day. They just don't have that capacity with Spirit now.

Doug

[Guest_Oersted_*]

Hope thwere wont be any millenium-bug-type problems when the Rovers move into three digit sols... 998-999-1000-*pling*-end-of-contact...

[diane]

I'm a bit more worried about 1024.